---
title: "Lit Review: Energetics"
author: "Kathleen Durkin"
date: "2024-06-20"
categories: ["pacific_oyster"]
format:
  html:
    toc: true
engine: knitr
bibliography: ../../../references.bib
---

The oyster project will involve evaluating some metric(s) of body condition or energy storage (e.g. glycogen content) in attempt to ID condition indicative of stress tolerance *before* the stress occurs. This necessitates some understanding of energetics in invertebrates (which I don't currently have) -- to the literature!

## Developmental cost theory

[@marshall_developmental_2020]

-   higher temperatures increase metabolic rate and decrease development time, but the extent to which temperature affects these factors is *different*, meaning overall costs of development increase with any deviation from optimal development temperature (above or below). At warmer temps, metabolic rate increases faster than development time can decrease

-   costs of development are more severely affected by temperature deviations than survival is.

-   temperature dependence of development rate is the parameter with greatest influence on the costs of development in relation to optimal temperature.

## Energy homeostasis to assess stress tolerance

[@sokolova_energy_2012]

The most basic description of energy balance can be summarized as

C = P + R + U + F

Consumption (energy acquired), Production (energy incorporated), Respiration (maintenance costs), U is excreted metabolism products (e.g. Urea), and unutilized Food energy (excreted as well)

-   "Importantly, the net energy exchange and energy balance of an organism depends not only on the amount of the available food, but also on the **rates of its incorporation and metabolic conversio**n that channel the energy flux to different processes."

![](https://ars.els-cdn.com/content/image/1-s2.0-S0141113612000712-gr1.jpg)

-   "the ability (or lack thereof) to sustain aerobic scope emerges as a major criterion that distinguishes between moderate and extreme stress"

    -   transition to anaerobiosis occurs because of limitations in oxygen uptake/transport

    -   could aerobic metabolism be a useful biomarker? How does one measure aerobic metabolism? I guess it wouldn't be super useful as a preemptive indicator of resiliance/preparedness/tolerance, since changes to aerobic metabolism happen *during* stress

-   [low-moderate stress (pejus):]{.underline} Compensation. Accelerated metabolism/ATP turnover to provide additional energy in support of cellular maintenance/damage repair, and accompanying increase in feeding or changes in energy allocation. Also often fueled by utilizing energy stores (e.g. glycogen and lipid stores).

    [extreme stress (pessimism):]{.underline} Conservation. Slow-down of metabolism and physiological activity to conserve energy resources and reduce accumulation of intracellular waste from compensatory activity. All available energy devoted to somatic maintenance, rather than growth, reproduction, or storage. In extreme cases, may enter metabolically arrested state, temporarily suppressing activity below maintenance levels to conserve energy until normal function becomes possible. **This metabolic arrest is particularly common in animals native to extreme environments (e.g. the intertidal)**
